X线检查肺动脉段凹陷（）
A.动脉导管未闭合并肺动脉高压
B.室间隔缺损
C.房间隔缺损
D.法洛四联症
E.动脉导管未闭
参考答案：D
a2和2a表示的意义相同。[ ]
From the top of the hill, we got a spectacular ____________ of San Francisco Bay and the city.
A．view
B．scene
C．scenery
D．sign
